Controllable pitch propeller



March 7, 1939. F. wv CALDWELL I 2,149,388

CONTROLLABLE P I TCH PROPELLER Filed Oct. 1, 1935 Patented Mar. 7,- 1939UNITED STATES PATENT OFFICE Frank W. Caldwell, Hartford, Conn., assignorto United Aircraft Corporation, East Hartford, Com, a corporation ofDelaware Application October 1, 1935, Serial No. 43,006 3 Claims. (Cl.170-163) This invention relates to improvements in controllable pitchpropellers and has particular reference to improvements in means fortemporarily restraining the controlling mechanism of a controllablepitch aeronautical propeller against changing the pitch angle of thepropeller.

An object of the invention lies in the provision of a light, simpleand,efiective means for positively restraining the pitch controlling.mecham nism from changing the pitch angle of the propeller during thetime the restraining mechanism is operative. l I

A further object resides in the provision of an electrically operatedvalve for restraining the 15 pitch controlling mechanism of acontrollable pitch propeller from changing the pitch angle of thepropeller during the time the electric valve actuating mechanism isoperative.

, Other objects and advantages will be apparent m as the descriptionproceeds.

In the accompanying drawing in which like reference numerals refer tosimilar parts I throughout there is illustrated, a suitable mechanicalembodiment of what is now considered ,5 to be the preferred form of theinvention. The

drawing, however, is for the purpose of illustration only and is not tobe taken as limiting the invention, the scope of which isto be measuredentirely by the scope of the appended claims.

a In the drawing,. the single figure is a vertical elevational view of acontrollable pitch propeller showing the application thereto of thedevice of the invention, certain portions of the propeller mechanismbeing broken away to better illustrate as the construction thereof, andthe device of the invention being illustrated in section.

For a" more complete disclosure of a suitable propeller mechanism withwhich the device of the invention may be associated, reference may 40 behad to my co-pending application Serial No. 656,533, filed February 13,1933, for Propellers.

Referring tothe drawing in detail the numeral Ill generally indicatesthe front or nose plate of a suitable power plant such as a radial aircooled 6 internal combustion engine. This front plate is provided with abearing receiving aperture I! through which projects a power shaft l4upon the projecting end of which is mounted the controllable pitchpropeller generally indicated at l l3. This propeller has a plurality ofhollow blades as indicated at It and 20, each blade being provided inthe hollow base or root end thereof with a cylindrical flanged sleeve asindicated at 32. These sleeves are rotatably mounted upon I radiallyprojecting arms 24 and 23 formed upon a spider having a centralcylindrical portion 23 non-rotatably fixed upon the projecting end ofthe shaft l4. The blades are retained upon the, spider arms 24 and 26against the action .of centrifugal force by means of thrust bearings asindicated at 30 which bear against the inturned ends 32 of a splitbarrel member 34. Arms, as indicated at 36 and 38, are non-rotatablysecured to the flanged base portions of the sleeves 22'of the propellerblades l8 and 20 respectively and 10 project forwardly from thepropeller blades substantially parallel to the axis of the shaft l4.Each ofthe' arms 36 and 38 is provided with a cam slot 40 extendingtherethrough for a purpose to be presently described, and each armcarries upon the outer or free end thereof, a counterweight 42. Thesecounterweights are so disposed with relation to the axes of the bladesl8 and and .the axis of the shaft l4 about which the propeller rotatesthat, upon rotation of the pro- 20 peller, the counterweights under theinfluence of centrifugal force tend to rotate the blades l8 and 20 in adirection to increase the pitch angle of the propeller blades.

A hollow piston 44 is secured upon the forward end of the cylindricalspider portion 28 so that its center line is coextensive with theprojection of the axis of the shaft l4 and a cylinder 46 is mounted forreciprocation upon the piston 44' and is provided upon diametricallyopposite sides 30 thereof with radially extending arms 48 which carrypins 50 which extend into the cam slots provided in the counterweightarms 36 and 38 to operatively connect the reciprocable cylinder 46 withthe counterweight arms so that an out-' 5 ward movement of the cylinder46 with respect to the piston 44 will exert a force upon thecounterweight. arms opposing the centifugal force of the counterweights42 to rotate 'the propeller blades l8 and 20 toward a low pitchposition. Hydraulic 40 fluid from a suitable source such as thelubricating pump of the engine, or-an'auxiliary pressure pump, issupplied to the space between the for-' ward end of the piston 44 andthe end wall 50 of the cylinder 46, through an axial bore in the 45shaft l4 and through the interior of the hollow piston 44. The engine isprovided with a carburetor not illustrated, which carburetor isadjustable in the usual manner to regulating the relative propor- ,surecorresponding to the various altitudes at which the engine is operated.The mixture controlling mechanism of the carburetor is adjusted by ahand lever 64 mounted in some location convenient to the operator of thevehicle upon which the engine and propeller are mounted and connectedwith the carburetor by a suitable link mechanism.

The customary method of adjusting the mixture control of an internalcombustion engine such as is ordinarily used for the propulsion ofaircraft consists in general of maintaining the engine throttle in afixed position and then adjustlng the mixture control lever until therevolutions per minute of the engine reach a maximum as indicated on atachometer visible to the operator. In some instances after the bestmixture ratio has been obtained, the mixture control lever may be movedslightly toward the lean or rich positions to either provide a leanmixture to give maximum fuel economy or a slightly rich mixture toprevent overheating of the engine cylinders. It is obvious that thismixture regulating operation must be carried out with a constant pitchangle setting'of the propeller blades as any change in the blade anglewill affect the revolutions per minute of the engine so that theoperator would be unable to tell at what mixture ratio the enginerevolutions were at the maximum rate per. minute. As the controllablepitch propeller automatically adapts its blade angle to the power outputof the engine to maintain constant the number of engine revohead of thevalve member generally indicated.

lutions per minute, in order to permit accurate mixture ratio adjustmentsome means must be provided to maintain the propeller blade angleconstant during the mixture adjusting operation. In the presentinvention this means takes the form of a suitable solenoid actuatedvalve generally indicated at 58, disposed within the hole .low piston 44in a position to control the flow of hydraulic fluid Ito and from thespace between the piston and the end wall.52 of the cylinder 46. Whenthe cylinder 46 is thus retained in fixed position relative to thepiston 44, the arms 36 and 38 are restrained against movement and thepropeller blades I8 and 28 are held at a fixed blade angle.

The valve 58 comprises a hollow cup shaped member 68 open at its forwardend and provided at its closed rearward end with a cylindrical reducedportion 62 which forms a casing for the at 64. 'The casing member 68 isprovided with an out-turned flange 66 which overlies a portion of theforward end of the piston 44 to provide a bearing surface for securingthe casing to the piston. Within the casing 68 there is a hollowcylindrical solenoid casing 68 enclosing a solenoid I8; Thesolenoid'casing 68 has an outer diameter less than the inner diameter ofthe casing 68 and is disposedwithin the casing 68 so that its exteriorsurface is annularly spaced from the interior surface of the casing 68as indicated at 12 to provide a passage for hydraulic fluid between thesolenoid casing and the cup shaped casing 68. The solenoid casing 68 isprovided at its rearward end with :an annular extension within which isformed a beveled valve seat 14 which cooperates with a similar valveseat 16 formed on the enlarged head portion of the valve 64. A pluralityof ports 18 extend through the reduced portion 62 of the casing 68 andthe extension on the solenoid casing to the space between the valveseats I4 and I6, and a plurality of ports 88 lead from this space intothe space between the solenoid casing and the cup shaped casing 68 toprovide a passage through the valve mechanism for bydraulic fluid whenthe valve is open. A coiled compression spring 82 is disposed between-anannular extension 84 upon the rear end of the valve head and the rearend of the annular extension formed on the solenoid casing 68 toresiliently urge the valve toward the open position illustrated in thedrawing. The valve is provided with an integral cylindrical armature 86which projects into a cylindrical bore provided in the solenoid casing68 so that when the solenoid I8 is energized the armature will be movedto the left as viewed in the figure to bring the valve seats 14 and I6into contact with each other and thus close the valve. A plate member 88overlies the forward end of the solenoid casing 68 and the flange 66 onthe casing 68, and is provided at its center with a plug 98 extendinginto the armature bore in the solenoid casing to increase the magneticflux within the bore. The flange 68 and the plate are apertured asindicated at 89 to provide a passage for hydraulic fluid from thespace12 to the space between the piston and the cylinder. The plug 98 isprovided with an axial bore or aperture 82 leading into the spacebetween the inner end of the plug and the adjacent end of the armature86 to relieve -any pressure that might build up in this space and tendto retard movements of the armature. A plurality of pressure releasebores 94 are also provided in the valve head to relieve any pressurethat might accumulate between the valve head and the end wall 96 of thevalve casing 62.

- The valve is maintained in fixed relation to the piston 44 by means ofa plurality of insulated screws as indicated at 88, and the solenoidleads I88 are connected to the ends of one pair of these screws at theends thereof which project into the space between the piston 44 and thecylinder 46. Electrical leads I82 are connected to the ends of thesescrews lying within the piston 44 and are led to respective contactrings I84 and I86 mounted in a ring 188 of insulating material securedupon the rear end of the cylindrical portion 28 of the propeller spider.The rings I86 and I88 are enclosed by an annular casing II8 rigidlysecured to the front plate I8 of the engine surrounding the aperturethrough which the shaft I4 projects. A pair of contact brushes H2 and H4are mounted in a block II6 of insulating material carried by the casingH8 and are spring pressed into contact with the'rings I84 and I86respectively in the usual manner. A pair of electrical conductors H8 andI28 extend from the brushes H2 and H4 respectively to the opposite sidesof a switch mounted upon the mixture control handle 54-, one of theconduits leading through a suitable source of electrical energy suchasthe battery I21. This switch comprises a contact button I22 secured tothe knob of the mixture control handle and a leaf spring I24 providedwith a contact point I26 secured to the stem portion of the handle andso positioned that the contact point I26 is in alignment with thecontact button I22 but is normally spaced therefrom. The switch isordinarily open, the solenoid I8 is deenergized and the valve 64 isurged to its open position by the spring 82, thus permitting automaticregulation of the blade angle by the ifsual speed responsive devicethrough which the hydraulic fluid is fed to the propeller controllingmechanism. When the operator grasps the mixture control lever 54 heincidentally bends the leaf spring I24 so that the switch contacts I22and ii. are closed. Thus, during the time that the mixture control isbeing adjusted the switcli is maintained closed, the solenoid 10 isenergized and the valve 64 is closed so that the propeller controllingmechanism is rendered inoperative to change the blade angle of thepropeller during the mixture regulating operation. When the operatorreleases the lever 54 the resiliency of I the leaf spring I24automatically opens the switch and restores the. propeller controllingmechanism to the'regulation oi the speed responsive mechscribed but thatsuch changes in the size, shape and arrangement of parts may be resortedto as come within the scope of the subjoined claims.

Having now described the invention so that others skilled in the. artmay clearly understand the same, what it is desired to secure by LettersPatent is as follows:

What it is claimed is:

1. In a controllable pitch propeller, a rotatable hub, a plurality ofpropeller blades mounted on said hub for rotational adjustment abouttheir respective axes, centrifugal means. for adjusting the pitch angleof said blades in one direction, hydraulic means carried by said hub foradjusting the pitch angle of said blades in the opposite direction,means for supplying fluid under pressure to said hydraulic means irom afluid pressure source remote from said propeller, a solenoid actuatedvalve carried by said hub operative to interrupt the flow 0t fluid toand from said hydraulic said hub to slide on said rings, a source oielectrical energy, a manually operable switch, and

1 electrical connections between said solenoid and said rings andbetweensaid brushes said source 01' electrical energy and said switch.

2. In a controllable pitch propeller, a rotatable 'hub, a plurality ofpropeller blades mounted on said hub for rotational adjustment abouttheir respective axes, centrifugal means for adjusting the pitch angleoi! said propeller blades in one direction, hydraulic means comprising apiston fixed on said hub and a cylinder slidable on said pistonoperatively connected with said blades for adjusting the pitch angle ofsaid blades in the opposite direction, a passage for fluid through saidpiston, a valve ands solenoid for actuating the same located in saidpiston to interrupt the flow of fluid through said passage, and remotecontrol means for energizing said solenoid.

3. In a controllable pitch propeller, a rotatable hub, a plurality ofpropeller blades mounted on said hub for rotational adjustment abouttheir respective axes, centrifugal means for increasing the pitch angleof said blades, hydraulic means for decreasing the pitch angle of saidblades said hydraulic means comprising a piston fixed on said hub and acylinder slidable on said piston and operatively connected with saidmeans, a solenoid actuated valve in said piston for controlling themovement 01' said cylinder by interrupting the flow oi fluid to and fromthe space between said cylinder and said piston, and remote controlmeans for energizing said solenoid.

centrifugal mam: w. CALDWELL.

